Servo system for airplanes and other vehicles



J. c, NEWTON May 25, 1942 SERVO SYSTEM FOR AIRPLANE'S AND OTHER VEHICLES.

Filed Dec. 21, 1939 4 Sheets -Sheet 1 INVENTOR fin CJVewZon May 266, 1942. J. c. fisw'rofl SERVO SYSTEM FOR AIRPLANES AIND OTHER VEHICLES 4 Sheets-Sheet 2 Filed Dec. 21, 1939 YINVENTOR I V 757v? C-Mwfiwp,

Maw Y.

' May 26, 1942. J. c. NEWTON SERVO SYSTEM FOR AIRPLANES AND OTHER VEHICLES Filed Decn 21, 19:59 4 Sheets-Sheet s INVENTOR I Jaim c JVwfon W 1942. J. c. NEWTON 2,284,298

SERVO SYSTEM FOR ILIRPLANES AND OTHER VEHICLES 4 Sheets-Sheet 4 Filed Dec. 21, 1539 n m 1 Y mm M M m w m Patented May 26, 1942 UNITED STATE s PATENT OFFICE" SERVO SYSTEM FOR AIRPLANES AND OTHER VEHICLES 7 Claims.

This invention relates to a servo motor or power multiplying system for relieving the operator of the greater portion of the manual labor of moving a control element on a dirigible vehicle, such as an airplane or motor car. It is now appreciated that in such a system, the natural movements and feel of the manually operated system which it aids should preferably beretained as largely as possible and, at the same time, complications involving the use of followback connections or special relays avoided. Especially is this true of the operation of the control surfaces on large aircraft. It is also important that in case of failure of the servo system, the operator may be able to move the control surface or device directly by hand and,

preferably, without first performing any additional operation, simply by continuing to exert pressure on the same control device as is used when the servo system is operating. By my invention I achieve all of the above purposes with a simple mechanism and without employing any additional follow-back mechanisms, either hydraulic or mechanical.

. My invention is also adapted for use in connection with automatic pilots for aircraft, espethe bell crank control lever and, in dotted lines, the first position which is opposite to that shown in full lines in Fig. 1, and the second or final position for a marked left turn.

Fig. 9 is a plan view showing a modified form of linkage connection between the control column, control surface and servo motor.

Fig. 10 shows still a further modification.

Fig. 11 is-an elevation, partly in section, of a further modification showing a rotary servo motor, such as an electric motor instead of the hydraulic engines of the other forms.

Fig. 12 is a sectional detail taken on line l2- l2 of Fig. 11.

Referring first to Fig. 1, I represents the primary impulse controller for the control device of the craft, in this case control surface 2, such 1 hydraulic servo motor, which may comprise two Referring to the drawings, showing several forms my invention may assume,

Fig. 1 is a diagrammatic plan view of my invention as applied to a hydraulic formof servo system for the control of one of the control surfaces in an aircraft.- I

Fig. 2 is a side elevation of the same, ,partly' in section.

Fig. 2-A is an enlarged detail of a portion .of Fig. 2, parts being in section.

Fig. 3 is a sectional view. through one ofthe control valves. v

Fig. -4 is a plan view of a modified form of the control with improved sensitivity.-

Fig, 5 is a side view of the form of the same,

partly in section.

Fig.6 is a detail of a portion of Fig. 5 with the .locking sleeve in a different position.

- operated sleeve of Fig. 5.

Fig. 8 is a plan view as in Fig. 1, but showing in full lines the neutral or normal'position' of 5.3

spaced single acting cylinders I and 8 with the piston rod 6 connecting the two pistons 1' and 8' thereof.

its normal position, the laterally extending arm 9 of the bell crank lever is perpendicular to the piston rod 6, as shown in full lines in Fig. 8,

and also in Fig. 4.. The other arm IU of the bell crank lever in this position is at substantially aright angle to the arm 9 and is linked at its left hand end to a slider l, on link II which of distributing valve l5, which controls the fiow of operating fluid to the cylinders 1 and 8.

The bell crank levers l2 and I3 are also connected at their other end by a link 2| to form a parallel linkage system.

In the normal or.closed position,'with. the arm 9 in the position shown in full lines in Fig. 8, the valve lies in the position shown in Fig. 3, with the ports closed so that the system is locked. If, however, the'valve is, rotated a few degrees clockwise in Fig. 3, port l6, connected to the. sump, will be connected through the channel. I! through the valve to the port l8 leading to cylinder 1, for instance. At the same time the' Obviously, a single cylinder double acting piston may be employed, if desired. In

of the cylinder the servo motor system.

8 to apply pressure thereto. n the other hand, a slight rotation in the counterclockwise direction will effect the reverse connection of the pressure source and sump to the cylinders I and I.

rod or other connecting means The connectin 22'to the control surface 2 is connected to an intermediate point 23 on the arm 2. This point is preferably nearer the pivot point '2 of the bell crank lever on thepiston rod 8 thanthe pivot '25 on rod 4 so that a force multiplication is secured for the manualcontrol, which may be further increased by the relative lengthof the lever] on the far side of pivot 3 as compared to its length between the pivot 3 and connection l to'link 4. As shown, the two -armssl and II of bell-crank i are secured to a sleeve 24' or hollow crank shaft journaled on cross pin 95 ex- "tending through the piston rod 6. Arm 9 is .shown as forked to furnish a journal on both .ends of pin 95.

' The operation of in Fig. 8, the system is locked andat rest. If the aviator desires to turn the rudder in the direction shown in Fig. 8, he moves the lever l clockwise. Thiscauses a-rotation of the bell crank lever 5 about the pivot 2! toward the first dotted position. since the piston is at that time locked, thereby moving the point 23 slightLv to the right. This causes a lowering of the link II' and the consequent rotation of the bell crank lever l3 and its connected valve in the counterclockwise direction to admit pressure oil to the cylinder I, thereby causing the movement'of the the system so far described. is as follows: In the .position shown in full lines nished by the servo system in proportion to the leverage system adopted.

It is quite evident that the sensitiveness of the device may be increased by increasing the length of the arm It as compared to that of the arm 2 and also its length as compared to that of arm ll of bell crank lever II. Such a modification is shown in Figs. 4 and 5, in-which the arm II is made longerthan the arm 0' and arm It made shorter. This figure also shows how the rudder may manually operated in case of failure of the valve l5 and the servo system. In this case, the manual lever I is linked at 4' to a sleeve 3| 'slidably mounted on the connecting rod 22' leading.to the control surface 2'. Said sleeve is shown as loosely' connected to the control rod 22' through-a pin and slot connection 3| and t2, the sleevebeing also linked to the arm t through a link 33. The arm 0' is again shown as pivoted as to prevent turning of the piston rod 8'. Preferably said pin is slightly below the link II in its normal position, the arm I! extending at a slightly obtuse angle-to the arm 9'. In this case,

' the bell crank levers I2 and is are again connected by a parallel link 2|, but neither is mounted directly on th stem ll of the valve,

but ll'is shown as coupled to the valve stem l4 through a link 38 and arm )1, by which further amplification of. movement is secured.

In this system (Figs. Land 5), as in the system of Figs. 1 and 8, the movement of the conpiston rod 8 to the right, carrying'with it pivot ment results in a rotation of the bell' cranklever 5 about the point so as to move the'rod22 .further'to the right and restore the arm 9 to its perpendicular position, as-shown -in the second vdotted line-position, and at the same time again' shows an intermediate position of the'partsfor counter-clockwise rudder movement.

Several important advantages of my invention will be apparent from the foregoing. One advantage is that although the servo system assists the aviator in moving the rudder, at thev same time the aviator feels the resistance to movement of the control member I proportional to the A resistance of the rudder to movement, since when the servo is actin the lever l rotates about the point 25 as a pivot and hence exerts a reactive force on the handle [equal to the difference in forces exerted on the pin 2| andpin 23.

Itshould also be understood that although, in describing Fig. 8, three distinct steps; are set .point 24 and the bell crank lever 5. This movely,- and further movement would be secured if the troller l' is opposed by the proportional component of the resistance of the surface 2',.since the sleeve 30 cannot rotate arm 2' around pivot point 35 without displacing pivot 23' and, therefore, displacing the rod 22' connected -.to the surface 2. In this system provision is made so that if the hydraulic system fails, the surface may still be moved from the hand controller I. A limited motion may of course be effected direct-' handle is moved far enough to bring the pin ll to the end of the slot :2, thereby tying the sleeve Ill-and therod 22' together fordirect movement by-handle I". Such a movement presupposes lateral displacement of the link 2', including the pivot 28, and therefore freedom of movement of the pistons. Since valve II has been opened by the initial movement of controller I, this would occur unless the fluid flow were blocked in the p p o pipi As a further safety de'vicesnd in' order to avoid the lost motion present in the above described system when being operated entirely by hand and also to secure the full range movement under these conditions, I may provide a bypass valve 32 betweenthe two working ends of the cylinders I and I, which is preferably automatically opened when the aviator eliminates the lost motion device. For this purpose I have shown Y a sleeve or collar ll .rotatably but non-slidably forth, in practice the movements of the hydraulic pistons follow so closely the movements of the handlever that the-two oc'cur practically together, and consequently the final movement of the rudder is at all times proportional to the displacement of the manual controller I, and the force supplied to move the same is mainly fur- 7-? ins. the

.mounted on the sleeve ll adjacent-the pin II and having a V-shaped slot ll therein. when the open end of said slot is adjacent the pin II,

the servo motor is in operation and the lost motion device operative. To throw the lost motion device out of operation, the operator turns.

the collar II by a handle ll to bring the V-noteh ll into engagement with the pin, thuseliminatlost motion. At the same time, gearing is provided between the collar and the bypass -valvef3 8to open the same under these condifl gearing is shown comprising a gear 43 on sleeve.

which carries handle 50 and meshes with; an ongated pinion 44 on the shaft of a bevel gear 45, meshing with a second bevel gear 46 on th shaft of the bypass valve 38.

Obviously, my invention may assume many different forms. In Fig. 9, the bell crank lever 5' is-retained, but the arm III", in this case, is formed as a segmental gear sector, the teeth 60 thereof loosely meshing with teeth on an elongated pinion 6| secured to the shaft of the valve The operation is therefore essentially the same since the lever 5' may move laterally with the piston 6 to which ity is pivotally secured, without turning the valve, thus causing movement of the valve I5 only when pivotal movement takes place. I A still further modification-is shown in Fig. 10.

. In this case, bell crank lever 5" may be conthereto as shown, .said links being connected at their outer ends to the arm 61 on the stem of the valve 15. An analysis of this linkage will show that movement of the piston alone will not effect movement of the valve but any rotation of between members 10 and II to'pull the latter the bell crank lever 5" about point 24" will rotate the valve as before. Action is, therefore, substantially the same as inthe other figures.

An application of my invention to a rotary system is shown in Figs. 11 and 12. In this case, two drums l0 and H are shown mounted with their axes in a common line AA, drum 10 being opera-ted from' a control column as by means of a cable 12, and drum H operating the control -si'1rface as by means of a cable I3. Each drum has an inwardly projecting pin 14 and 15 on the inner surface thereof, each of which enters loosely a hole in a cross lever 16 extending between the drums. The inner end of said lever is' pinned to a shaft 11 joumalled' in the long sleeve 18 extending at right angles. to the axis of rotation of the drums and secured to a sleeve .19 extend- 14 column; (2) at an intermediate point 15 to h the control. surface; and (3) to a part (sleeve 18) driven from a servo motor, which in this case is a motor 8| turning through pinion 82, a

large gear 83, the hub 84 of which is pinned to the sleeve 18 carrying sleeve I8.

In case of rotation of lever I6 about the axis of shaft 11, motion is transmitted to the controller 85 of the motor 8| in some suitable manner as by means of asmall crank "-pinned to the bottomjof the shaft" and connected by 'link'8'l to a rod 88 slidablyand freely mounted within the sleeve 19. To the outer end of said shaft 88, is a channelled collar 89 which upon axial movement rotates a-forked lever 88 about pivot point ill to move the controller of motor 8|. A consideration of Figs. 11 and 12 will show that ,as long as drums I0 and II are moved together, lever I6 will be bodily moved, that is, translated, broadly speaking, and still maintain its normal position shown in' Fig. 12, i. e., without being rotated about any one of the pivot pins l4, 15 or 11. When, however, the control column moves the drum 10 downwardly in Fig. 12, for instance, lever 16 will be rotated clockwise either about the present axis of shaft I5 if there is a heavy load on the drum H, or about the'present axis of shaft 11 in case there is little or no load on the drum. In either case, clockwise rotation of the lever 16 will turn the shaft 11 and thus operate the controller 85 through the linkage 86, 81, 90 and thus operate the motor 8| to rotate the gear 83 and sleeve 88, and with it the arm 18 in a downward direction in Fig. 12. This will continue until the lever 16 is again restored to its perpendicular position between the drums, as shown in Fig. 12. This mechanism therefore operates on the same'general principles'as the mechanism described in connection with the other figures, i. e., the lever is rotated about an axis intersecting the same for operating the control valve or other controller, but bodily movement or translation of the lever does not affect the controller. In this form of the invention, as in the form shown in Figs. 4 and 5, it is possible to move the controlled surface by hand from the hand control member 10 in case the servo motor fails, the lever 16 acting in this case as a link around with the former as the former is rotated by hand.

. ings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim" and desire to secure by Letters Patent is:

1. In a servo motor system for vehicles, a servo motor for turning the steering or other control element thereof in either direction, a controller therefor movable in either direction from its standstill position to cause said motor to operate in either direction, a lever pivoted on a part movable with said motor, manual means for rotating said lever about said pivot point, said lever being also connected adjacent said pivot point to said steering element, and a connection between said lever and said controller permitting free translation or bodily movement of said lever with said part connected to said motor without affecting said controller, but causing movement of said controller upon rotation of said lever.

2. In a servo motor system for vehicles, a motor for turning the control surface in either direction, a controller therefor movable in either direction from its normal shut-off position to cause said motor to operate in one direction or the other, a bell crank lever pivoted on a part movable with said motor, manual means for moving said lever connected at a remote point to one arm of said lever, a near point on said lever being connected to the control surface, and a sliding connection between the arm of said lever and said controller, so constructed and arranged that said controller is not actuated on translation of the pivot point of said bell-crank but only upon displacement of said lever whereby, upon initial manual rotation of said lever, the controller is/moved to operate the servo motor until said bell crank lever is displaced sufllciently to rotate about said remote point through an angle sufiicient to retum said controller to its shut-oft position. v

3. In a fluid servo motor system for vehicles, a fluid pressure motor for turning the control surface in either direction, an operating valve therefor movable in either direction from its normal shut-off position to cause pressure fluid flow in either direction to said motor, a bell crank lever pivoted on a part movable with said motor, manual means for moving said lever connected at a remote point to one arm of said lever,

a nearer point on said lever being connected to point through an angle sumcient to again close said valve, and a normally detached coupling between said manual means and said steering ele- ,ment connection so constructed and arranged that when coupled, said lever is prevented from rotating and it and said connection are trans-r lated to turn the element by hand.

5. A servo motor, system for vehicles as claimed in claim 4 having means for operating said coupling'torender it operative and inoperative, and

automatic means for bypassing said fluid motor when said coupling is rendered-operative. 6. A power booster adapted for displacement through substantial angles in either direction i and in which the hand controller moves with and supplies a portion of the power to move the load element, comprising a rotary servo motor for the control surface. a connection between the other arm of said lever and said valve, so constructed and arranged that upon manual rotation of' said leve'r, the valve is moved to operate ,the servo motor until said bell crank lever is dis- -placed sufliciently to rotate about said remote point through an angle suflicient'to close said valve, and a lost motion connection between said manual means and the connection to said control surface permitting hand operation on failure of the servo motor. v

4. In a fluid servo motor system for vehicles,

a fluid pressure motor for turning the control surface in either direction, an operating valve therefor movable in either direction from its normal shut-off position to cause pressure fluid now in either direction to said motor, a bell crank lever pivoted ona part movable with said motor, manual means for moving said lever connected at a remote point to one. arm of said lever, a nearer point on said lever being connected to the control surface, a connection between the other arm of said lever and said valve. so con-' structed and arranged that upon manual rotation of said le'ver, the valve is opened to operate the servo motor until said bell crank lever is displaced sufllciently'to rotate about said remote turning the load element ineither, direction through any desired angle, a controller therefor flrst member and extending radially thereof, and

means'slidable axially along the axis of said first member and linked to the inner endof said bellcrank lever for moving said controller, whereby the operator may cause movement of said element through said servo motor through any distance in either direction by maintaining the manual'controller angularly ahead of said first member.

7. A power booster as claimed, in claim 6, in

which said bell-crank lever, in case of power failure, serve as a link between said .two members whereby the load element may be driven directly from the manual 'control element in case of powerfailure.

' JOHN C. NEWTON. 

